Electric bed warmer and method for producing same



April 10, 1951 G. w. CREE 2, 8,467

ELECTRIC BED WARMER AND METHOD FOR PRODUCING SAME Filed Sept. 15, 1947 Patented Apr. 10, 1951 UNITED STATES PATENT OFFICE ELECTRIC BED WARMER AND METHOD FOR PRODUCING SAME 6 Claims.

the user lies, there are four principal factors which must be considered to make the device satisfactory for its intended use. First, the bed warmer must be smooth and flexible, and devoid of bulges and lumps, otherwise the same I would present considerable discomfort to the user. Next, the bed warmer should be strong and durable, in order that the same may Withstand the normal abuse received when positioned upon the mattress of the bed, due to the movement of the A body thereon, and due to the rumpling or mussing encountered during the making of the bed with the bed warmer positioned thereon. Thirdly, the electrical heating element within the bed warmer must be well insulated electrically to protect the user from possible electric shock, even in the event that water be spilled upon or absorbed within the bed warmer. Lastly, devices of this character must necessarily be porous and moisture absorbent, in order to allow free passage of perspiration from the body of a person lying upon the same. In the manufacture of so called electric blankets, the first of these factors may be more or less disregarded, due to the fact that the blanket type of bed warmer is usually positioned over the body of the user, and the presence of bulges is not so noticeable. Likewise, the factor of flexibility is not of utmost importance with the blanket type of warmer, due to the fact that the warmer does not have to yield under the weight of the body when positioned above the user.

It is therefore, the primary object of this invention to provide a structurally simple and efficient bed warmer of the type adapted to be positioned upon the mattress of the bed and upon which the user may sleep, the same being characterized by its flexibility, its smoothness and freedom from undesirable bulges and lumps, its ability to freely transmit moisture, and at the same time be safe in operation by eliminating the hazard of electrical shock; and lastly, its ability to withstand rough usage encountered during normal operation.

It is another object of the present invention to provide simple and efllcient methods for producing bed warmers of this type, wherein a continuous electrical resistance element having a flexible and meltable outer insulating covering is embedded between a pair of fabric sheets, comprising the outer jacket of the bed warmer, and the assembly passed between a pair of heated compression rolls in a substantially continuous operation to melt the outer meltable insulation of the resistance element and fuse the same into the mesh of the fabric sheets, thus anchoring the resistance element and at the same time uniting the previously separate sheets of fabric.

It is still another object of this invention to provide an improved method for anchoring the current supply line, associated with the electrical resistance element, to the jacket of the bed warmer to prevent accidental separation of the lead wire from the jacket, and the possibility of damaging the internal resistance element.

For a further and more detailed understanding of the present invention and the additional objects and advantages thereof, reference is made to the following description and the accompanying drawings wherein:

Fig. l is a diagrammatic view illustrating the substantially continuous operation by which my improved bed warmers are formed;

Fig. 2 is a diagrammatic view, in perspective, illustrating one form of apparatus which may be utilized in carrying out my improved methods for the formation of electrically heated bed warmers;

Fig. 3 is an enlarged perspective view of a segment of the insulated resistance wire utilized in bed warmers of the type formed in accordance with thepresent invention.

Fig. 4 is an enlarged fragmentary vertical sectional view taken through a finished bed warmer and disclosing a single segment of the electrical resistance element of the bed warmer.

Fig. 5 is a perspective view of one corner of my improved bed warmer, with the outer jacket broken away to disclose the method of anchoring the associated current-supplying lead wire within the outer jacket of the bed warmer.

Fig. 6 is a fragmentary elevational view of one end of the electrically heated compression rolls utilized in the formation of my improved bed warmers.

With reference to the drawings, it will be seen that the present invention makes use of two sheets of substantially porous fabric material, designated by the numerals .ID and H. Such fabric material may advantageously be cotton muslin, linen, or wool. Disposed transversely 3 between the two sheets of fabric in substantially co-extensive zig-zag fashion, is a continuous coil of electrical resistance wire l2. The resistance wire I2 is provided with an insulating covering I 3 formed from a tough yet flexible high-temperature insulating material of the type known commercially as Formvar. In addition to the insulating coverin l3, the wire [2 is provided with a second and outer covering [4 of a suit,- able flexible and dielectric bonding material which melts or softens appreciably at a temperature well above the maximum operating temperatures of the resistance wire l2, but at temperatures substantially below that which would be detrimental to or would cause deterioration of the fabric sheets I and H. Such a temperature should approximate 300 degrees Fahrenheit. Many materials are suitable for use in 4 material with the interposed insulated coils of resistance wire pass between the two heated rolls l8 and I9, the outer insulating covering ll of the resistance wire is melted and pressed into the mesh of the two fabric sheets, to form a flexible, yet strong adhesive weld between the resistance wire and the two sheets, at the same time uniting the two fabric sheets to eliminate the necessity for forming pockets in, or for sewing the resistance wire into position between the layers of the fabric material. From the compression rolls [8 and IS, the welded assembly is wound about the wind-up roll 20, from whence the assembly may be subsequently taken to be cut in desired lengths in accordance with the dimensions of the finished, bed Warmer.

In initially passing the two sheets of fabric I between the compression rolls I8 and I9, the

this capacity which possess the desired temperature properties, which are moisture resistant, possess gooddielectric. properties, and yet retain their flexibility and strength after having been melted. For example, unvulcanized rubber, certain unpolymerized thermosetting synthetic resins, such as the phenolics and ureas, and lastly, and preferably, certain thermoplastic synthetic resins, such as the polyvinyls, polystyrenes, and acrylic type of resins. It has been found through practice, that the use of a thermoplastic type of resin known as polyvinyl chloride, as the outer bonding material for the resistance wire l2, has produced excellent results, in that this material can readily be softened at a temperature of 300 degrees Fahrenheit, possesses extremely good dielectric and moisture resistant properties, and yet retains its tough flexibility indefinitely after having been melted.

In the formation of my improved bed warmers, the fabric sheets I 0 and H are assembled in layers with the resistance wire l2 and its associated insulating jackets disposed in zig-zag fashion between the two sheets, and the assembly passes between a pair of heated compression rolls, in order that the outer covering M of in sulating and bonding material may be melted, pressed, and fused within the mesh of the fabric sheet to unite the two separate sheets and to anchor the resistance wire therebetween. The fusing of the outer insulating covering [4 into the mesh of the fabric sheets forms, after 0001- ing, a strong and tough, yet flexible weld between the resistance wire or heating element and the two sheets which comprise the outer jacket ofthe bed warmer.

Figs. 1 and 2 of the drawing illustrate in diagrammatic form one type of apparatus suitable for use in the formation of my improved electrically heated bed Warmer. The assembly generally comprises two cloth-supplying rolls l5 and I6 upon which bolts of the fabric material are wound, a spool i! which contains the double insulated resistance wire, a pair of spaced electrically heated compression rolls I8 and I9, a

wind-up roll 20, and a mechanically operated wire-feeding arm 2|. In operation, two continuous sheets of the fabric material are led around the respective rolls l8 and l9,,while the resistance wire,.fed from the spool H, is arranged in zig-zag fashion transversely of the lower .sheet and held at its respective ends or loops upon the outer face of the lower roll l9 by radially projecting spring-pressed fingers 22 about which the resistance wire is looped by the feed arm 2| in synchronized relation with the rotation of thelower roll l9, As the two sheets of fabric width of the sheets is such that the outer edges are allowed to overlap the compression rolls, so that ample material is afforded at the outer edges of the sheets, in order that the same may be hemmed together to complete the outer jacket of the bed warmer. Before hemming, the assembled sheets and coil are cut into desired lengths, with the severed ends of the resistance wire being electrically connected by soldering with a current supply line or wire 23. Fig. 5 of the drawing discloses this operation, with the lead wire 23 being introduced between the two sheets of fabric at one corner of the warmer. Before connectin the lead wire 23 with the respective ends of the resistance coil, the lead wire is provided at its jacket-adjoining end with an extra tubular covering 26 of the meltable bonding material, of the type utilized as the outer covering of the resistance wire, and after connection between the lead wire and the resistance coils, the corner of the two fabric sheets is caused to overlap this extra covering, the same being heated and pressed, in order that the outer covering may be melted and welded into the corner between the two fabric sheets, thus forming a flrm but flexible weld between the end of the lead wire and the two sheets of fabric, thereby preventing accidental separation of the lead wire from the outer jacket of the bed warmer, and further preventing any possibility of damaging displacement of the heating ele- As an alternative method of anchoring the lead wire 23 to the outer jacket of the warmer, the end of the lead wire may be covered with a jacket of the meltable bonding material, and placed between two separate pieces of cloth or fabric to be melted and fused therewith. In this procedure, the two separate pieces of cloth are. then sewn between the main sheets of fabric which comprise the outer jacket of the bed warmer after" the ends of the lead wire have been electrically connectedwith the ends of the heating element. tain advantages in handling, and in the inspection of the finished joint before finally finishing the bed warmer.

Instead of applying heat and pressure to the assembly of sheets and heating element, the bonding or welding of the outer insulating covering I 4 with thetwo plies orsheetsof the outer jacket may be accomplished by applyinga suitable liquid s'olvent'to the assembly through the outer sheets, which solvent is capable of partially dissolving the outer covering it of the resistance wire to effect an adhesive Weld between the material of the outer covering and the fabric sheets, which This procedure provides for cer- 5 weld would be confined to the region of the heating element only, and would not effect the overall porosity of the finished bed warmer.

In view of the foregoing, it will be seen that the present invention provides a structurally 5 simple yet mechanically eflicient bed warmer which is characterized by its flexibility, its comfort to the user, and its safety in operation, provided by the increased electrical insulation afforded by the outer jacket of bonding material applied directly to the resistance element and functioning both as a bonding agent and as an insulating jacket for the resistance wire. Further, my invention sets forth new and novel methods for the formation of such bed warmers, wherein considerable yardage of the fabric material having the necessary resistance wire embedded therein is produced in a substantially continuous operation, with the integrally formed assembly being cut in accordance with the desired dimensions of a finished bed warmer after initially bonding andthe anchoring of the heating element between the sheets of the outer jacket thereof. Also, the present invention provides a novel and eificient means for anchoring the associated current supply line directly to the material from which the outer jacket of the bed warmer is formed, in order to prevent dislocation of either the lead wire or the internal resistance wire.

Although the use of two fabric plies or sheets is preferred, it Will be understood that the present invention contemplates anchoring or bonding the electrical resistance wire in either insulated or uninsulated form to a single sheet of porous fabric material, which, after bonding, may be placed within an envelope or outer jacket and sewn therein to provide a finished bed warmer or pad.

While present specific embodiments of the present invention have been disclosed in detail, it will be manifest that various modifications as to details of construction, and materials utilized, may be accomplished without departing from the spirit of the invention or the scope of the following claims.

I claim:

1. A flexible, porous, electrically heated warming device comprising a sheet of porous fabric material, a continuous convoluted grid of electrical resistance wire, and a flexible outer covering of fusible dielectric material carried on said resistance wire and firmly uniting the same with said sheet, said fusible dielectric material being integrally thermoplastically joined to said sheet and being confined substantially to the regions of said resistance wire whereby to prevent impairment to the over-all porosity of said sheet.

2. A flexible electrical heating device comprising a plurality of porous fabric plies, a continuous electrical resistance wire disposed in relatively spaced transverse convolutions between a pair of adjacent plies, and an outer covering of flexible dielectric material carried on said resistance wire and firmly uniting the same throughout its 5 length with said pair of plies, said outer covering being fused within the fabric of said plies and being confined substantially to the regions of said resistance wire whereby to prevent impairment to the porosity of said plies.

3. In an electrically heated moisture permeable flexible warming article, an outer jacket comprising upper and lower plies of porous fabric material, and a flexible electrical heatingelement positioned between the upper and lower plies of said jacket, said heating element being arranged in longitudinally spaced convolutions throughout the length of said plies and having a flexible outer covering of dielectric bonding material firmly welded into the fabric of said plies and mechanically joining the same only in the regions of said heating element, whereby to prevent impairment to the porosity of said plies.

4. In the construction of flexible, moisture permeable, electrically heated bed warmers; the steps which comprise placing a continuous length of electrical resistance wire having an outer covering of flexible, dielectric heat-fusible material thereon between a pair of longitudinally converging porous fabric sheets, applying heat and pressure to said sheets and said resistance wire at the line of convergence of said sheets'to melt the outer covering of said resistance wire and force the same into the fabric of said sheets, and thereafter permitting said material to cool and rigidly join said resistance wire and said sheets in the regions of said resistance wire.

5. A flexible, porous, electrically heated bed warmer comprising a sheet of porous fabric material; an electrical heating element including a continuous length of electrical resistance wire arranged in spaced convolutions substantially throughout the length of said sheet; and an outer covering of flexible, fusible, dielectric bonding material carried on said resistance wire and thermoplastically joined to said sheet in the regions of said resistance wire only whereby to firmly anchor said resistance wire to said sheet without impairing the overall porosity of said sheet.

6. In the construction of a flexible, electrically heated bed warmer, the method which comprises positioning a strand of electrical resistance wire having an outer covering of flexible dielectric bonding material thereon transversely of and adjacent to a porous fabric sheet; moving said sheet and strand of wire longitudinally and looping said strand at one end and passing the same transversely across said sheet to form a second strand disposed in longitudinally spaced relation to said first-named strand; fusing the outer covering of said resistance wire; applying compressive forces to the outer covering of said resistance wire and fabric sheet to embed the outer covering material within the fabric of said sheet in the regions of said resistance wire; and thereafter permitting the outer covering of said resistance wire to set and firmly anchor the strands of resistance wire to said fabric sheet in transversely disposed longitudinally spaced seams throughout substantially the entire length of said sheet.

GEORGE W. CRISE REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,384,467 Homan July 12, 1921 1,963,554 McDill June 19, 1934 2,025,586 Hall Dec. 24, 1935 2,126,833 Strinberger Aug. 16, 1938 2,251,697 Van Daam et a1. Aug. 5, 1941 2,298,181 Stranszky Oct. 6, 1942 2,402,631 Hull June 25, 1946 2,423,196 MacKendrick July 1, 1947 FOREIGN PATENTS Number Country Date 428,036 Great Britain J an. 31, 1934 

